Northern Water Snake: Nerodia sipedon

The Northern Watersnake (Nerodia sipedon sipedon) is a medium-sized, non-venomous, Colubrid snake of Eastern North America.  It is found in a variety of aquatic habitats such as lakes, rivers, and wetlands as well as man-made ditches and retention ponds.

How do I Identify a Northern Watersnake?

Northern Watersnakes typically have dark dorsal (back) bands that are present on the anterior (towards the head) portion of the body that change to alternating dorsal (back) and lateral (side) blotches. Their ventral (belly) scales usually have dark half-moon shaped markings on them. Be aware that there can be a lot of variation within this general description! (Many watersnakes can look very different from this!)

Unfortunately, watersnakes are often confused and misidentified as
venomous Cottonmouths or Copperheads. Some simple characters are
present that can help the non-herpetologist distinguish between
watersnakes and their venomous counterparts. First, is the general
shape of their head, although this is not the most reliable. Venomous
snakes such as the Cottonmouth and Copperheads have a triangular shaped
head that is very wide at the base due to the presence of the venom
glands. However, to the untrained (and unfamiliar eye), defensive
posturing (flatening and widening of the head and body) of many species
of watersnakes can be misleading. Fortunately, two other characters are
present on the head of the animal to help the confused observer. Non-venomous watersnakes have round pupils, not eliptical shaped (cat
eyes), like those of venomous species. Finally, on a Northern Watersnake, there will be no heat sensing PIT organ on the either side of the head between
the eye and nostril. In addition to the head characteristics, Northern watersnakes typically swim with their body below the water (just the head above the surface), while venomous snakes like the Cottonmouth swim on top of the water.

What do Northern Watersnakes eat?

Watersnakes eat primarily aquatic prey items such as small fishes and
amphibians (frogs and salamanders), but on rare occasion have been
found to eat invertebrates (worms, leeches, crayfish) and small mammals
(shrews and voles).  Recently, some populations have started feeding
upon the introduced Round goby, an invasive species.Snake diets can also differ based on age or sex. 

What eats Northern Watersnakes ?

Predators of the Northern Watersnake include birds, raccoons, opossums, foxes, snapping turtles, and other snakes. 

How do Northern Watersnake Reproduce?

Northern Watersnakes are live-bearing snakes! They mate in the early Spring and give birth in late
summer to several pencil sized young. The number of babies an
individual female watersnake can produce in a litter (or clutch) is
highly dependent on a number of factors (like how much food is available), but
is most strongly associated with her own body size. In other words, the
bigger the female, the more babies she can have!

Speaking of
bigger, female Northern Watersnakes are quite a bit bigger than males in this species. The
maximum body size reported in Conant and Collins for a Northern
Watersnake was 1500 mm (almost 5 feet).

What should I do if I find a Northern Watersnake?

Look, but don't touch! Even though they are not venomous, watersnakes are considered an aggressive species and will bite if handled. If you do pick one up and get bitten, don't panic! Just treat the small wound like any other scrape or scratch (wash with soap, bandage if needed).

References

• Conant, R. and J. T. Collins. 1998. Reptiles and Amphibians: Eastern and Central North America. Peterson Field Guides (series), 3rd ed. expanded, Houghton Mifflin Co., New York, New York, 616 pp.
• Gibbons, J.W. and M.E. Dorcas. 2004. North American Watersnakes: A Natural History. University of Oklahoma Press, Norman. 438pp.